1. Field of the Invention
This invention relates to optical measurement apparatus and is particularly although not exclusively applicable to measurement of dimensions of shaft-like components such as diameters, ovalities, lengths between shoulders, concentricities, straightness and thread features. Dimensions of non-shaft-like components can also be measured provided they are suitable for optical projection.
2. Background of the prior art
U.K. Patent Specification No. 2,058,344 discloses an electro-optical apparatus for inspecting an elongate workpiece such as a camshaft having spaced lobes which is supported and turned between centres. A sensor head is provided comprising a light source, a lens for forming an image of an edge of a camshaft lobe on a photo-diode array and a read out unit. For components of widely varying dimensions such as valves, several sensors adapted to the particular dimensions to be measured have to be provided. Thus the apparatus is not immediately adaptable to measurement of different components of widely varying sizes.
U.K. Patent Application No. 2,078,945 also discloses an optical measurement system in which photo-detectors are used. The apparatus is particularly concerned with the methods of analysing the light pattern produced on a photo-detector array and no provision is made for rendering the apparatus readily adaptable to suit different components of different dimensions.